a gyatt is a big booty cause it's how saying "gyatt damn" sounds.
"GYATTTT THATS A BIGGGG BOOTY"
its when you see a fat ass like a really fat ASS it came from yourRAGE its a short term for GOD DAMN!!
jonnys GYATT!!!!! is soooooooooooooooooooo big, like this
"Gyatt" is a term to define a well-rounded bottom or perfectly shaped ass. Usually used in a joking manner.
That man over there has a GYATT